Question 379740
The working equation is always distance = rate x time, or d = rt.
If the cars travel for the same time t, and we call the speed of the slower car r, the faster car travels at a speed of r+40.
So 
150=rt
350=(r+40)t
Let us solve the first one for t and substitute it into the second, thus solving for r, the speed of the slower car.  So...
t = 150/r
and
{{{350=(r+40)(150/r)}}}
{{{350r=150(r+40)}}}
{{{350r=150r + 6000}}}
{{{200r = 6000}}}
{{{r=30}}} km/hr